Target Enzyme And Mtrrcde Of Efflux System At The Same Time Mutations In Fluoroquinolone-resistant Neisseria Gonorrhoeae Occurs

Objective: To evaluate the susceptibility of Neisseria gonorrhoeae to five antimicrobial agents in Taiyuan of Shanxi.The occurrence of ciprofloxacin resistance among Neisseria gonorrhoeae strains isolated and the frequency and patterns of mutations in gyrA and parC genes in these isolates.The role of MtrRCDE efflux system in gonococcal resistance to fluoroquinolones.High occurrence of simultaneous mutations in target enzymes and MtrRCDE efflux system in Quinolone-Resistant Neisseria gonorrhoeae.Methods: (1)Disk diffusion method was used to test susceptibility of antimicrobial agents including penicillin, tetracycline, ciprofloxacin, ceftriaxone, spectinomycin. Thirty-five N. gonorrhoeae were collected to test the minimum inhibitory concentrations(MICs) of ciprofloxacin by E test method.(2)The gyrA,parC genes and the inverted sequence within the mtrR promoter region were amplified by PCR.(3)The amplicons were directly analyzed by DNA sequencing.Results: (1)The positivity rates of resistant isolates to penicillin, tetracycline, ciprofloxacin, ceftriaxone, spectinomycin were 68.6%,74.3%,100%,11.4%,2.9%. Positivity rates of multiple-resistant isolates to five antimicrobial agents were 80%.(2)35 fluoroquinolone-resistant strains had a single or double-point mutation(s) in gyrA gene and mutations in gyrA were Ser-91â†'Phe and Asp-95â†'Gly.25 high-level fluoroquinolone-resistant strains(MIC≥4mg/L) had double-point mutations in gyrA gene and a single or multi-point mutation(s) in parC gene.The most common mutations in parC were Ser-87â†'Arg and Tyr-104â†'Tyr.(3)All of the 28 strains which were multiple resistance had mutations in a 13bp inverted sequence positioned within the mtrR promoter region,and the same mutation exhibited A/T a single base pair deletion in this region.(4)The frequency of mutation in gyrA,parC,and the mtrR promoter was 100%,94.3%,77.1%.Seventy-seven percent of strains carried mutations in both gyrA and the mtrR promoter.Conclusion: (1)Positivity rate of multiple-resistance increases rapidly,and the resistance to ciprofloxacin also increases rapidly.Spectinomycin and ceftriaxone should be the first choice in the treatment of gonorrhes at present in Taiyuan of Shanxi.(2)Mutations in gyrA and/or parC genes play an important role in the development of fluoroquinolone resistance in N.gonorrhoeae.ParC gene was the most important reason of ciprofloxacin in high-level resistance in Neisseria gonorrhoeae. (3)A single base pair deletion in a 13bp inverted sequence positioned within the mtrR promoter region is associated with multiple resistance.(4)Simultaneous mutations in fluoroquinolone target enzymes and the MtrRCDE efflux system as a fluoroquinolone-resistant mechanism in N.gonorrhoeae.